Pulmonary hypertension (or PAH) is described as increased blood pressure in the heart’s pulmonary arteries due to constriction, blockage, or damage to the pulmonary blood vessels. The blood vessels become stiff, inflamed, and thick, which causes reduced blood flow to the lungs. PAH presents initially as shortness of breath upon exertion, constant fatigue, and dizziness.
When pulmonary hypertension progresses, the shortness of breath (dyspnea) is noticed even without exertion or exercise. According to health care professionals PAH is sub-classified into six other classes, depending on the causative agent (or underlying cause) responsible:
1. Group (I): PAH caused by unknown factors
In the larger percentage of individuals, the cause of PAH is unknown (idiopathic), other causes could be due to prescription drugs like methamphetamines, congenital heart disease, a familial genetic mutation that is inherited from one generation to the next, or chronic liver disease. Additionally, PAH is linked to HIV infection, portal hypertension, thyroid gland disorder, glycogen storage disorders, sickle cell disease, pulmonary venous occlusive disease, and connective tissue diseases like scleroderma. Some of the symptoms of pulmonary hypertension PAH include chest pain, dyspnea, and edema of the ankles.
2. Group (II): PAH due to existing disease in the left side of the heart
The left side of the heart is the primary power source of the heart. It pumps blood to the rest of the body apart from the lungs. Therefore, when the left side of the heart is diseased, it becomes less effective. Consequently, the heart’s right side will have to pump the blood at higher pressures to meet the body’s oxygen requirements. This, in turn, will cause pulmonary hypertension. Examples of diseases that may affect the left side of the heart are left ventricular failure or left-sided heart blood vessel disease, which could affect either the aortic or the mitral valve.
3. Group (III): PAH due to lung disease
Lung diseases are a common cause of pulmonary hypertension. When the lungs are damaged, there is an increased demand for oxygen, which causes the blood increased pulmonary blood pressure. Lung diseases associated with pulmonary hypertension include pulmonary fibrosis caused by tuberculosis, obstructive sleep apnea, chronic obstructive pulmonary disease (COPD), and interstitial lung illness.
4. Group (IV): PAH caused by chronic clotting of the blood
This type of pulmonary hypertension is also known as chronic thromboembolic pulmonary hypertension (CTEPH). CTEPH occurs when blood clots in the pulmonary vessels. The thrombi may attach itself to the pulmonary vessels’ walls, thus restricting blood flow to the lungs. Another explanation to this is as a result of scar tissue due to damaged blood vessels that facilitate blood clot formation. Additionally, blood clotting disorders might be a cause of pulmonary hypertension. Pulmonary hypertension due to blood clots usually resolves naturally or with anticoagulant medication.
5. Group (V): PAH caused by other medical conditions
Pulmonary hypertension may occur as a symptom of an underlying medical condition. Inflammatory diseases like vasculitis, sarcoidosis, and autoimmune inflammatory disease may affect the pulmonary arteries, thus potentiating pulmonary hypertension. Additionally, tumors in the lungs may press the pulmonary arteries causing pulmonary hypertension. Other diseases that may potentiate a pulmonary hypertensive crisis include blood disorders like polycythemia vera and thrombocythemia, Eisenmenger syndrome, histiocytosis X, and kidney diseases.
6. Additional risk factors for PAH
Old age, smoking, obesity, increased exposure to asbestos, and chronic use of opioid-containing drugs like cocaine predisposes an individual to develop pulmonary hypertension. Additionally, some families acquire pulmonary hypertension as an inherited disease due to genetic mutation or genetic congenital heart disease. Living in high altitude areas may also potentiate pulmonary hypertension.
